Human amine transporter

ABSTRACT

A Human amine transporter polypeptide and DNA (RNA) encoding such polypeptide and a procedure for producing such polypeptide by recombinant techniques is disclosed. Also provided are methods for detecting agonists and antagonists to such polypeptide and the use of agonists and antagonists for treating diseases related to the under-expression and over-expression of the Human amine transporter of the present invention. Also disclosed are methods for detecting mutations in the nucleic acid sequence encoding the polypeptide and for detecting altered levels of the soluble form of the polypeptide.

FIELD OF THE INVENTION

This invention relates to newly identified polynucleotides, polypeptides encoded by such polynucleotides, the use of such polynucleotides and polypeptides, as well as the production of such polynucleotides and polypeptides. More particularly, the polypeptide of the present invention is a human amine transporter. The invention also relates to inhibiting the action of such polypeptides.

RELATED ART

Neurosensory and neuromotor functions are carried out by neurotransmission. Neurotransmission is the conductance of a nerve impulse from one neuron, called the presynaptic neuron, to another neuron, called the postsynaptic neuron, across the synaptic cleft. Transmission of the nerve impulse across the synaptic cleft involves the secretion of neurotransmitter substances. The neurotransmitter is packaged into vesicles in the presynaptic neuron and released into the synaptic cleft to find its receptor at the postsynaptic neuron. Transmission of the nerve impulse is normally transient.

An essential property of synaptic transmission is the rapid termination of action following neurotransmitter release. For many neurotransmitters, including catecholamine, serotonin, and certain amino acids (e.g., gamma-aminobutyric acid (GABA), glutamate and glycine), rapid termination of synaptic action is achieved by the uptake of the neurotransmitter into the presynaptic terminal and surrounding glial cells. This rapid re-accumulation of a neurotransmitter is the result of re-uptake by the presynaptic terminals.

At presynaptic terminals, the various molecular structures for re-uptake are highly specific for such neurotransmitters as choline and the biogenic amines (low molecular weight neurotransmitter substances such as dopamine, norepinephrine, epinephrine, serotonin and histamine). These molecular apparatuses are termed transporters. These transporters move neurotransmitter substances from the synaptic cleft back across the cell membrane of the presynaptic neuron into the cytoplasm of the presynaptic terminus and therefore terminate the function of these substances. Inhibition or stimulation of neurotransmitter uptake provides a means for modulating the effects of the endogenous neurotransmitters.

Re-uptake of neurotransmitter substances by the transporters may be sodium-dependent. For instance, the GABA transporter is a member of the recently described sodium-dependent neurotransmitter transporter gene family. These transporters are transmembrane receptor complexes having an extracellular portion, a transmembrane portion and an intracellular portion. A significant degree of homology exists in the transmembrane domains of the entire family of sodium-dependent neurotransmitter transporter proteins, with considerable stretches of identical amino acids, while much less homology is apparent in the intracellular and extracellular loops connecting these domains. The extracellular loop in particular seems to be unique for each transporter. This region may contribute to substrate and/or inhibitor specificities.

Identifying the novel amine transporter of the present invention and elucidating the structural and functional distinctions between different types of transporters is important in understanding the cellular and molecular bases of behavior and disease.

SUMMARY OF THE INVENTION

The polypeptide of the present invention has been putatively identified as an amine transporter. This identification has been made as a result of amino acid sequence homology to the rat amine transporter.

In accordance with one aspect of the present invention, there is provided a novel mature polypeptide which is a human amine transporter, as well as biologically active and diagnostically or therapeutically useful fragments, analogs and derivatives thereof.

In accordance with another aspect of the present invention, there are provided isolated nucleic acid molecules encoding a human amine transporter, including mRNAs, DNAs, cDNAs, genomic DNAs as well as analogs and biologically active and diagnostically or therapeutically useful fragments and derivatives thereof.

In accordance with yet a further aspect of the present invention, there is provided a process for producing such polypeptide by recombinant techniques comprising culturing recombinant prokaryotic and/or eukaryotic host cells, containing a human amine transporter nucleic acid sequence, under conditions promoting expression of said protein and subsequent recovery of said protein.

In accordance with yet a further aspect of the present invention, there is provided a process for utilizing such polypeptide, or polynucleotide encoding such polypeptide for screening for agonists and antagonists and ligands to such polypeptide.

In accordance with yet a further aspect of the present invention, there is provided a method for utilizing such agonists for stimulating the amine transporter uptake of neurotransmitter ligands for the treatment of diseases related to under-expression of the amine transporter or over-expression of the ligand.

In accordance with yet another aspect of the present invention, there is also provided a process for using antagonists for inhibiting the amine transporter uptake of neurotransmitter ligands for the treatment of diseases related to over-expression of the amine transporter or under-expression of the ligand.

In accordance with yet a further aspect of the present invention, there are provided antibodies against such polypeptides.

In accordance with yet a further aspect of the present invention, there are also provided nucleic acid probes comprising nucleic acid molecules of sufficient length to specifically hybridize to human amine transporter sequences.

In accordance with still another aspect of the present invention, there are provided diagnostic assays for detecting diseases related to the under-expression and over-expression of the amine transporter polypeptide and mutations in the nucleic acid sequences encoding such polypeptide.

In accordance with yet a further aspect of the present invention, there is provided a process for utilizing such polypeptides, or polynucleotides encoding such polypeptides, for in vitro purposes related to scientific research, synthesis of DNA and manufacture of DNA vectors.

These and other aspects of the present invention should be apparent to those skilled in the art from the teachings herein.

BRIEF DESCRIPTION OF THE FIGURES

The following drawings are illustrative of embodiments of the invention and are not meant to limit the scope of the invention as encompassed by the claims.

FIGS. 1A-1E illustrate the cDNA sequence (SEQ. ID NO:1) and corresponding deduced amino acid sequence (SEQ. ID NO:2) of the human amine transporter of the present invention. The standard one-letter abbreviations for amino acids are used. Sequencing was performed using a 373 Automated DNA sequencer (Applied Biosystems, Inc.). Sequencing accuracy is predicted to be greater than 97% accurate.

FIGS. 2A-2B are an illustration of an amino acid homology alignment between the amine transporter and a rat amine transporter (SEQ ID NO:2) (retrieved from Genbank public database).

BRIEF DESCRIPTION OF THE INVENTION

The amine transporter (SEQ ID NO:9) of the present invention may be responsible for re-uptake of one or any of the amine neurotransmitters present in mammalian cells. Examples of such amine transporters include dopamine, norepinephrine, epinephrine, serotonin and histamine, and other amino acid transmitters, including GABA, glycine and glutamate.

In accordance with an aspect of the present invention, there is provided an isolated nucleic acid (polynucleotide) which encodes for the mature polypeptide having the deduced amino acid sequence of FIG. 1 (SEQ ID No. 2) or for the mature polypeptide encoded by the cDNA of the clone deposited as ATCC Deposit No. 75980 on Dec. 16, 1994 at the American Type Culture Collection, 12301 Parklawn Drive, Rockville, Md. 20852.

A polynucleotide encoding a polypeptide of the present invention may be obtained from a variety of human tissues. The polynucleotide of this invention was discovered in a cDNA library derived from a human adrenal gland tumor. It is structurally related to the amine transporter family. It contains an open reading frame encoding a protein of 470 amino acid residues. The protein exhibits the highest degree of homology to the rat amine transporter with 80% identity and 86% similarity over a 468 amino acid stretch.

The polynucleotide of the present invention may be in the form of RNA or in the form of DNA, which DNA includes cDNA, genomic DNA, and synthetic DNA. The DNA may be double-stranded or single-stranded, and if single stranded may be the coding strand or non-coding (anti-sense) strand. The coding sequence which encodes the mature polypeptide may be identical to the coding sequence shown in FIG. 1 (SEQ ID No. 2) or that of the deposited clone or may be a different coding sequence which coding sequence, as a result of the redundancy or degeneracy of the genetic code, encodes the same mature polypeptide as the DNA of FIG. 1 (SEQ ID No. 2) or the deposited cDNA.

The polynucleotide which encodes for the mature polypeptide of FIG. 1 (SEQ ID No. 2) or for the mature polypeptide encoded by the deposited cDNA may include only the coding sequence for the mature polypeptide or the coding sequence for the mature polypeptide (and optionally additional coding sequence) and non-coding sequence, such as introns or non-coding sequence 5' and/or 3' of the coding sequence for the mature polypeptide.

Thus, the term "polynucleotide encoding a polypeptide" encompasses a polynucleotide which includes only coding sequence for the polypeptide as well as a polynucleotide which includes additional coding and/or non-coding sequence.

The present invention further relates to variants of the hereinabove described polynucleotides which encode for fragments, analogs and derivatives of the polypeptide having the deduced amino acid sequence of FIG. 1 (SEQ ID No. 2) or the polypeptide encoded by the cDNA of the deposited clone. The variant of the polynucleotide may be a naturally occurring allelic variant of the polynucleotide or a non-naturally occurring variant of the polynucleotide.

Thus, the present invention includes polynucleotides encoding the same mature polypeptide as shown in FIG. 1 (SEQ ID No. 2) or the same mature polypeptide encoded by the cDNA of the deposited clone as well as variants of such polynucleotides which variants encode for a fragment, derivative or analog of the polypeptide of FIG. 1 (SEQ ID No. 2) or the polypeptide encoded by the cDNA of the deposited clone. Such nucleotide variants include deletion variants, substitution variants and addition or insertion variants.

As hereinabove indicated, the polynucleotide may have a coding sequence which is a naturally occurring allelic variant of the coding sequence shown in FIG. 1 (SEQ ID No. 1) or of the coding sequence of the deposited clone. As known in the art, an allelic variant is an alternate form of a polynucleotide sequence which may have a substitution, deletion or addition of one or more nucleotides, which does not substantially alter the function of the encoded polypeptide.

The polynucleotides of the present invention may also have the coding sequence fused in frame to a marker sequence which allows for purification of the polypeptide of the present invention. The marker sequence may be a hexahistidine tag supplied by a pQE-9 vector to provide for purification of the mature polypeptide fused to the marker in the case of a bacterial host, or, for example, the marker sequence may be a hemagglutinin (HA) tag when a mammalian host, e.g. COS-7 cells, is used. The HA tag corresponds to an epitope derived from the influenza hemagglutinin protein (Wilson, I., et al., Cell, 37:767 (1984)).

The present invention further relates to polynucleotides which hybridize to the hereinabove-described sequences if there is at least 50% and preferably 70% identity between the sequences. The present invention particularly relates to polynucleotides which hybridize under stringent conditions to the hereinabove-described polynucleotides. As herein used, the term "stringent conditions" means hybridization will occur only if there is at least 95% and preferably at least 97% identity between the sequences. The polynucleotides which hybridize to the hereinabove described polynucleotides in a preferred embodiment encode polypeptides which retain substantially the same biological function or activity as the mature polypeptide encoded by the cDNA of FIG. 1 (SEQ ID No. 1) or the deposited cDNA.

The deposit(s) referred to herein will be maintained under the terms of the Budapest Treaty on the International Recognition of the Deposit of Micro-organisms for purposes of Patent Procedure. These deposits are provided merely as convenience to those of skill in the art and are not an admission that a deposit is required under 35 U.S.C. §112. The sequence of the polynucleotides contained in the deposited materials, as well as the amino acid sequence of the polypeptides encoded thereby, are incorporated herein by reference and are controlling in the event of any conflict with any description of sequences herein. A license may be required to make, use or sell the deposited materials, and no such license is hereby granted.

The present invention further relates to a human amine transporter polypeptide which has the deduced amino acid sequence of FIG. 1 (SEQ ID No. 2) or which has the amino acid sequence encoded by the deposited cDNA, as well as fragments, analogs and derivatives of such polypeptide.

The terms "fragment," "derivative" and "analog" when referring to the polypeptide of FIG. 1 (SEQ ID No. 2) or that encoded by the deposited cDNA, means a polypeptide which retains essentially the same biological function or activity as such polypeptide. Thus, an analog includes a proprotein which can be activated by cleavage of the proprotein portion to produce an active mature polypeptide.

The polypeptide of the present invention may be a recombinant polypeptide, a natural polypeptide or a synthetic polypeptide, preferably a recombinant polypeptide.

The fragment, derivative or analog of the polypeptide of FIG. 1 (SEQ ID No. 2) or that encoded by the deposited cDNA may be (i) one in which one or more of the amino acid residues are substituted with a conserved or non-conserved amino acid residue (preferably a conserved amino acid residue) and such substituted amino acid residue may or may not be one encoded by the genetic code, or (ii) one in which one or more of the amino acid residues includes a substituent group, or (iii) one in which the mature polypeptide is fused with another compound, such as a compound to increase the half-life of the polypeptide (for example, polyethylene glycol). Such fragments, derivatives and analogs are deemed to be within the scope of those skilled in the art from the teachings herein.

The polypeptides and polynucleotides of the present invention are preferably provided in an isolated form, and preferably are purified to homogeneity.

The term "isolated" means that the material is removed from its original environment (e.g., the natural environment if it is naturally occurring). For example, a naturally-occurring polynucleotide or polypeptide present in a living animal is not isolated, but the same polynucleotide or polypeptide, separated from some or all of the coexisting materials in the natural system, is isolated. Such polynucleotides could be part of a vector and/or such polynucleotides or polypeptides could be part of a composition, and still be isolated in that such vector or composition is not part of its natural environment.

The present invention also relates to vectors which include polynucleotides of the present invention, host cells which are genetically engineered with vectors of the invention and the production of polypeptides of the invention by recombinant techniques.

Host cells are genetically engineered (transduced or transformed or transfected) with the vectors of this invention which may be, for example, a cloning vector or an expression vector. The vector may be, for example, in the form of a plasmid, a viral particle, a phage, etc. The engineered host cells can be cultured in conventional nutrient media modified as appropriate for activating promoters, selecting transformants or amplifying the human amine transporter genes. The culture conditions, such as temperature, pH and the like, are those previously used with the host cell selected for expression, and will be apparent to the ordinarily skilled artisan.

The polynucleotides of the present invention may be employed for producing polypeptides by recombinant techniques. Thus, for example, the polynucleotide may be included in any one of a variety of expression vectors for expressing a polypeptide. Such vectors include chromosomal, nonchromosomal and synthetic DNA sequences, e.g., derivatives of SV40; bacterial plasmids; phage DNA; baculovirus; yeast plasmids; vectors derived from combinations of plasmids and phage DNA, viral DNA such as vaccinia, adenovirus, fowl pox virus, and pseudorabies. However, any other vector may be used as long as it is replicable and viable in the host.

The appropriate DNA sequence may be inserted into the vector by a variety of procedures. In general, the DNA sequence is inserted into an appropriate restriction endonuclease site(s) by procedures known in the art. Such procedures and others are deemed to be within the scope of those skilled in the art.

The DNA sequence in the expression vector is operatively linked to an appropriate expression control sequence(s) (promoter) to direct mRNA synthesis. As representative examples of such promoters, there may be mentioned: LTR or SV40 promoter, the E. coli. lac or trp, the phage lambda P_(L) promoter and other promoters known to control expression of genes in prokaryotic or eukaryotic cells or their viruses. The expression vector also contains a ribosome binding site for translation initiation and a transcription terminator. The vector may also include appropriate sequences for amplifying expression.

In addition, the expression vectors preferably contain one or more selectable marker genes to provide a phenotypic trait for selection of transformed host cells such as dihydrofolate reductase or neomycin resistance for eukaryotic cell culture, or such as tetracycline or ampicillin resistance in E. coli.

The vector containing the appropriate DNA sequence as hereinabove described, as well as an appropriate promoter or control sequence, may be employed to transform an appropriate host to permit the host to express the protein.

As representative examples of appropriate hosts, there may be mentioned: bacterial cells, such as E. coli, Streptomyces, Salmonella typhimurium; fungal cells, such as yeast; insect cells such as Drosophila S2 and Spodoptera Sf9; animal cells such as CHO, HEK, COS or Bowes melanoma; adenoviruses; plant cells, etc. The selection of an appropriate host is deemed to be within the scope of those skilled in the art from the teachings herein.

More particularly, the present invention also includes recombinant constructs comprising one or more of the sequences as broadly described above. The constructs comprise a vector, such as a plasmid or viral vector, into which a sequence of the invention has been inserted, in a forward or reverse orientation. In a preferred aspect of this embodiment, the construct further comprises regulatory sequences, including, for example, a promoter, operably linked to the sequence. Large numbers of suitable vectors and promoters are known to those of skill in the art, and are commercially available. The following vectors are provided by way of example. Bacterial: pQE70, pQE60, pQE-9 (Qiagen), pBS, pD10, phagescript, psiX174, pbluescript SK, pbsks, pNH8A, pNH16a, pNH18A, pNH46A (Stratagene); ptrc99a, pKK223-3, pKK233-3, pDR540, pRIT5 (Pharmacia). Eukaryotic: pWLNEO, pSV2CAT, pOG44, pXT1, pSG (Stratagene) pSVK3, pBPV, pMSG, pSVL (Pharmacia). However, any other plasmid or vector may be used as long as they are replicable and viable in the host.

Promoter regions can be selected from any desired gene using CAT (chloramphenicol transferase) vectors or other vectors with selectable markers. Two appropriate vectors are PKK232-8 and PCM7. Particular named bacterial promoters include lacI, lacZ, T3, T7, gpt, lambda P_(R), P_(L) and trp. Eukaryotic promoters include CMV immediate early, HSV thymidine kinase, early and late SV40, LTRs from retrovirus, and mouse metallothionein-I. Selection of the appropriate vector and promoter is well within the level of ordinary skill in the art.

In a further embodiment, the present invention relates to host cells containing the above-described constructs. The host cell can be a higher eukaryotic cell, such as a mammalian cell, or a lower eukaryotic cell, such as a yeast cell, or the host cell can be a prokaryotic cell, such as a bacterial cell. Introduction of the construct into the host cell can be effected by calcium phosphate transfection, DEAE-Dextran mediated transfection, or electroporation (Davis, L., Dibner, M., Battey, I., Basic Methods in Molecular Biology, (1986)).

The constructs in host cells can be used in a conventional manner to produce the gene product encoded by the recombinant sequence. Alternatively, the polypeptides of the invention can be synthetically produced by conventional peptide synthesizers.

Mature proteins can be expressed in mammalian cells, yeast, bacteria, or other cells under the control of appropriate promoters. Cell-free translation systems can also be employed to produce such proteins using RNAs derived from the DNA constructs of the present invention. Appropriate cloning and expression vectors for use with prokaryotic and eukaryotic hosts are described by Sambrook, et al., Molecular Cloning: A Laboratory Manual, Second Edition, Cold Spring Harbor, N.Y., (1989), the disclosure of which is hereby incorporated by reference.

Transcription of the DNA encoding the polypeptides of the present invention by higher eukaryotes is increased by inserting an enhancer sequence into the vector. Enhancers are cis-acting elements of DNA, usually about from 10 to 300 bp that act on a promoter to increase its transcription. Examples including the SV40 enhancer on the late side of the replication origin bp 100 to 270, a cytomegalovirus early promoter enhancer, the polyoma enhancer on the late side of the replication origin, and adenovirus enhancers.

Generally, recombinant expression vectors will include origins of replication and selectable markers permitting transformation of the host cell, e.g., the ampicillin resistance gene of E. coli and S. cerevisiae TRP1 gene, and a promoter derived from a highly-expressed gene to direct transcription of a downstream structural sequence. Such promoters can be derived from operons encoding glycolytic enzymes such as 3-phosphoglycerate kinase (PGK), α-factor, acid phosphatase, or heat shock proteins, among others. The heterologous structural sequence is assembled in appropriate phase with translation initiation and termination sequences. Optionally, the heterologous sequence can encode a fusion protein including an N-terminal identification peptide imparting desired characteristics, e.g., stabilization or simplified purification of expressed recombinant product.

Useful expression vectors for bacterial use are constructed by inserting a structural DNA sequence encoding a desired protein together with suitable translation initiation and termination signals in operable reading phase with a functional promoter. The vector will comprise one or more phenotypic selectable markers and an origin of replication to ensure maintenance of the vector and to, if desirable, provide amplification within the host. Suitable prokaryotic hosts for transformation include E. coli, Bacillus subtilis, Salmonella typhimurium and various species within the genera Pseudomonas, Streptomyces, and Staphylococcus, although others may also be employed as a matter of choice.

As a representative but nonlimiting example, useful expression vectors for bacterial use can comprise a selectable marker and bacterial origin of replication derived from commercially available plasmids comprising genetic elements of the well known cloning vector pBR322 (ATCC 37017). Such commercial vectors include, for example, pKK223-3 (Pharmacia Fine Chemicals, Uppsala, Sweden) and GEM1 (Promega Biotec, Madison, Wis., U.S.A.). These pBR322 "backbone" sections are combined with an appropriate promoter and the structural sequence to be expressed.

Following transformation of a suitable host strain and growth of the host strain to an appropriate cell density, the selected promoter is induced by appropriate means (e.g., temperature shift or chemical induction) and cells are cultured for an additional period.

Cells are typically harvested by centrifugation, disrupted by physical or chemical means, and the resulting crude extract retained for further purification.

Microbial cells employed in expression of proteins can be disrupted by any convenient method, including freeze-thaw cycling, sonication, mechanical disruption, or use of cell lysing agents, such methods are well know to those skilled in the art.

Various mammalian cell culture systems can also be employed to express recombinant protein. Examples of mammalian expression systems include the COS-7 lines of monkey kidney fibroblasts, described by Gluzman, Cell, 23:175 (1981), and other cell lines capable of expressing a compatible vector, for example, the C127, 3T3, CHO, HEK, HeLa and BHK cell lines. Mammalian expression vectors will comprise an origin of replication, a suitable promoter and enhancer, and also any necessary ribosome binding sites, polyadenylation site, splice donor and acceptor sites, transcriptional termination sequences, and 5' flanking nontranscribed sequences. DNA sequences derived from the SV40 splice, and polyadenylation sites may be used to provide the required nontranscribed genetic elements.

The human amine transporter polypeptide can be recovered and purified from recombinant cell cultures by methods including ammonium sulfate or ethanol precipitation, acid extraction, anion or cation exchange chromatography, phosphocellulose chromatography, hydrophobic interaction chromatography, affinity chromatography, hydroxylapatite chromatography and lectin chromatography. Protein refolding steps can be used, as necessary, in completing configuration of the mature protein. Finally, high performance liquid chromatography (HPLC) can be employed for final purification steps.

The polypeptides of the present invention may be a naturally purified product, or a product of chemical synthetic procedures, or produced by recombinant techniques from a prokaryotic or eukaryotic host (for example, by bacterial, yeast, higher plant, insect and mammalian cells in culture). Depending upon the host employed in a recombinant production procedure, the polypeptides of the present invention may be glycosylated or may be non-glycosylated. Polypeptides of the invention may also include an initial methionine amino acid residue.

Fragments of the full length human amine transporter gene may be used as a hybridization probe for a cDNA library to isolate the full length gene and to isolate other genes which have a high sequence similarity to the gene or similar biological activity. Probes of this type generally have at least 20 bases. Preferably, however, the probes have at least 30 bases and generally do not exceed 50 bases, although they may have a greater number of bases. The probe may also be used to identify a cDNA clone corresponding to a full length transcript and a genomic clone or clones that contain the complete human amine transporter gene including regulatory and promotor regions, exons, and introns. As an example of a screen comprises isolating the coding region of the human amine transporter gene by using the known DNA sequence to synthesize an oligonucleotide probe. Labeled oligonucleotides having a sequence complementary to that of the gene of the present invention are used to screen a library of human cDNA, genomic DNA or mRNA to determine which members of the library the probe hybridizes to.

This invention provides a method for determining amine neurotransmitters which are transported by the human amine transporter of the present invention. An example of an assay which will identify these neurotransmitters comprises infecting mammalian cells with recombinant vaccinia virus strain VTF-7 encoding a T7 RNA polymerase and following such infection with liposome-mediated transfection with the amine transporter gene through the use of a vector, for example, pBSSKII(-). Controlled transfections are also done with equivalent amounts of vector alone. Assays are performed eight hours following transfection in modified Krebs-Ringer-HEPES buffer. Cells are then incubated with ³ H! neurotransmitter (for example, GABA, dopamine, serotonin, etc.). Uptake is stopped by placing the cells on ice. Cells are solubilized in one percent SDS, and the amount of radioactivity accumulated is determined by liquid scintillation counting. A significant amount of uptake determines that the particular neurotransmitter is taken up by the human amine transporter of the present invention by determining background using control transfections with pBSSKII for each assay and subtracting the values obtained from the signals determined for the specific amine neurotransmitters.

This invention also provides a method of detecting expression of an amine transporter on the surface of a cell by detecting the presence of mRNA coding for an amine transporter. This method comprises obtaining total mRNA from the cell using methods well-known in the art and contacting the mRNA so obtained with a nucleic acid probe of at least 15 nucleotides and which is capable of specifically hybridizing with a sequence included within the sequence of a nucleic acid molecule encoding a human amine transporter, under hybridizing conditions, detecting the presence of mRNA hybridized to the probe, and thereby detecting the expression of the amine transporter by the cell. Hybridization of probes to target nucleic acid molecules such as mRNA molecules employs techniques well known in the art. However, in one embodiment of this invention, nucleic acids are extracted by precipitation from lysed cells and the mRNA is isolated from the extract using a column which binds the poly-A tails of the mRNA molecules. The mRNA is then exposed to radioactively labelled probe on a nitrocellulose membrane, and the probe hybridizes to and thereby labels complementary mRNA sequences. Binding may be detected by autoradiography or scintillation counting. However, other methods for performing these steps are well known to those of skill in the art.

Alternatively, an antibody directed to the human amine transporter may be employed under conditions permitting binding of the antibody to the transporter, and detecting the presence of the transporter on the surface of the cell. Such a method may be employed for determining whether a given cell is defective in expression of the amine transporter. Detection methods include fluorescent markers bound to the antibodies.

The invention also provides a method for determining whether a compound not known to be capable of specifically binding to a human amine transporter can specifically bind to the human amine transporter, which comprises contacting a mammalian cell comprising a plasmid adapted for expression in a mammalian cell which plasmid further comprises a DNA which expresses the amine transporter on the cell surface with the compound under conditions permitting binding of ligands known to bind to the amine transporter, detecting the presence of any compound bound to the mammalian amine transporter, the presence of bound compound indicating that the compound is capable of specifically binding to the human amine transporter.

This invention also provides a method of screening drugs to identify drugs which specifically interact with, and bind to a human amine transporter on the surface of a cell which comprises contacting a mammalian cell which expresses the human amine transporter on the surface of a cell with a plurality of drugs, detecting those drugs which bind to the cell, and thereby identifying drugs which specifically interact with, and bind to, the human amine transporter.

The present invention further provides a method for identifying agonist or antagonist compounds to the human amine transporter of the present invention by the employment of competition assays. An example of such an assay for identifying antagonists comprises contacting a neuronal cell which expresses the human amine transporter on the surface thereof with a known neurotransmitter, in the presence of a potential compound to determine the amount of neurotransmitter transported. Controls may also be prepared in the absence of the potential compound and the amount of amine neurotransmitter transported by the cell upon comparison to the control cell indicates if the potential compound stimulated transport or inhibited transport of the labeled amine neurotransmitter by the transfected mammalian cell.

Examples of human amine transporter antagonists include an antibody directed to the human amine transporter which comprises, for example, a monoclonal antibody directed to an epitope of a human amine transporter present on the surface of the cell. These antibodies are useful to detect the presence of human amine transporters or to inhibit the function of the transporters in humans.

Another potential antagonist is an antisense construct prepared using antisense technology. Antisense technology can be used to control gene expression through triple-helix formation or antisense DNA or RNA, both of which methods are based on binding of a polynucleotide to DNA or RNA. For example, the 5' coding portion of the polynucleotide sequence, which encodes for the mature polypeptides of the present invention, is used to design an antisense RNA oligonucleotide of from about 10 to 40 base pairs in length. A DNA oligonucleotide is designed to be complementary to a region of the gene involved in transcription (triple helix--see Lee et al., Nucl. Acids Res., 6:3073 (1979); Cooney et al, Science, 241:456 (1988); and Dervan et al., Science, 251:1360 (1991)), thereby preventing transcription and the production of human amine transporter. The antisense RNA oligonucleotide hybridizes to the mRNA in vivo and blocks translation of the mRNA molecule into the human amine transporter polypeptide (antisense--Okano, J. Neurochem., 56:560 (1991); Oligodeoxynucleotides as Antisense Inhibitors of Gene Expression, CRC Press, Boca Raton, Fla. (1988)). The oligonucleotides described above can also be delivered to cells such that the antisense RNA or DNA may be expressed in vivo to inhibit production of human amine transporter.

Potential antagonists also include a soluble form of a human amine transporter, e.g. a fragment of the transporter, which binds to the neurotransmitter and prevents it from interacting with the human amine transporter.

Potential antagonists further include a small molecule which binds to and occupies the extracellular portion of the human amine transporter thereby making the human amine transporter inaccessible to the neurotransmitter such that transport is inhibited. Examples of small molecules include but are not limited to small peptides or peptide-like molecules.

This invention additionally provides a method of treating an abnormal condition related to an excess of amine transporter activity which comprises administering to a subject the antagonist as hereinabove described along with a pharmaceutically acceptable carrier in an amount effective to block binding of naturally occurring substrates to the amine transporters and thereby alleviate the abnormal condition. Examples of abnormal conditions include epilepsy, schizophrenia, depression, cognitive impairment, anxiety and migraine headaches.

The invention also provides a method of treating abnormal conditions related to an under-expression of amine transporter activity which comprises administering to a subject an amount of the agonist described above in combination with a pharmaceutically acceptable carrier, in an amount effective to enhance binding of naturally occuring substrates to the amine transporter and thereby alleviate the abnormal conditions. Some examples of abnormal conditions are Parkinson's disease and Alzheimer's disease.

The soluble form of the human amine transporter, and agonists and antagonists may be employed in combination with a suitable pharmaceutical carrier. Such compositions comprise a therapeutically effective amount of the transporter, agonist or antagonist and a pharmaceutically acceptable carrier or excipient. Such a carrier includes but is not limited to saline, buffered saline, dextrose, water, glycerol, ethanol, and combinations thereof. The formulation should suit the mode of administration.

The invention also provides a pharmaceutical pack or kit comprising one or more containers filled with one or more of the ingredients of the pharmaceutical compositions of the invention. Associated with such container(s) can be a notice in the form prescribed by a governmental agency regulating the manufacture, use or sale of pharmaceuticals or biological products, which notice reflects approval by the agency of manufacture, use or sale for human administration. In addition, the pharmaceutical compositions may be employed in conjunction with other therapeutic compounds.

The pharmaceutical compositions may be administered in a convenient manner such as by the oral, topical, intravenous, intraperitoneal, intramuscular, subcutaneous, intranasal or intradermal routes. The pharmaceutical compositions are administered in an amount which is effective for treating and/or prophylaxis of the specific indication. In general, they are administered in an amount of at least about 10 μg/kg body weight and in most cases they will be administered in an amount not in excess of about 8 mg/Kg body weight per day. In most cases, the dosage is from about 10 μg/kg to about 1 mg/kg body weight daily, taking into account the routes of administration, symptoms, etc.

The human amine transporter and agonists and antagonists which are polypeptides may also be employed in accordance with the present invention by expression of such polypeptides in vivo, which is often referred to as "gene therapy."

Thus, for example, cells from a patient may be engineered with a polynucleotide (DNA or RNA) encoding a polypeptide ex vivo, with the engineered cells then being provided to a patient to be treated with the polypeptide Such methods are well-known in the art. For example, cells may be engineered by procedures known in the art by use of a retroviral particle containing RNA encoding a polypeptide of the present invention.

Similarly, cells may be engineered in vivo for expression of a polypeptide in vivo by, for example, procedures known in the art. As known in the art, a producer cell for producing a retroviral particle containing RNA encoding the polypeptide of the present invention may be administered to a patient for engineering cells in vivo and expression of the polypeptide in vivo. These and other methods for administering a polypeptide of the present invention by such method should be apparent to those skilled in the art from the teachings of the present invention. For example, the expression vehicle for engineering cells may be other than a retrovirus, for example, an adenovirus which may be used to engineer cells in vivo after combination with a suitable delivery vehicle.

This invention is also related to the use of the human amine transporter gene as part of a diagnostic assay for detecting diseases or susceptibility to diseases related to the presence of mutations in the human amine transporter genes. Such diseases are related to under-expression of the human amine transporter.

Individuals carrying mutations in the human amine transporter gene may be detected at the DNA level by a variety of techniques. Nucleic acids for diagnosis may be obtained from a patient's cells, such as from blood, urine, saliva, tissue biopsy and autopsy material. The genomic DNA may be used directly for detection or may be amplified enzymatically by using PCR (Saiki et al., Nature, 324:163-166 (1986)) prior to analysis. RNA or cDNA may also be used for the same purpose. As an example, PCR primers complementary to the nucleic acid encoding the human amine transporter protein can be used to identify and analyze human amine transporter mutations. For example, deletions and insertions can be detected by a change in size of the amplified product in comparison to the normal genotype. Point mutations can be identified by hybridizing amplified DNA to radiolabeled human amine transporter RNA or alternatively, radiolabeled human amine transporter antisense DNA sequences. Perfectly matched sequences can be distinguished from mismatched duplexes by RNase A digestion or by differences in melting temperatures.

Genetic testing based on DNA sequence differences may be achieved by detection of alteration in electrophoretic mobility of DNA fragments in gels with or without denaturing agents. Small sequence deletions and insertions can be visualized by high resolution gel electrophoresis. DNA fragments of different sequences may be distinguished on denaturing formamide gradient gels in which the mobilities of different DNA fragments are retarded in the gel at different positions according to their specific melting or partial melting temperatures (see, e.g., Myers et al., Science, 230:1242 (1985)).

Sequence changes at specific locations may also be revealed by nuclease protection assays, such as RNase and S1 protection or the chemical cleavage method (e.g., Cotton et al., PNAS, U.S.A., 85:4397-4401 (1985)).

Thus, the detection of a specific DNA sequence may be achieved by methods such as hybridization, RNase protection, chemical cleavage, direct DNA sequencing or the use of restriction enzymes, (e.g., Restriction Fragment Length Polymorphisms (RFLP)) and Southern blotting of genomic DNA.

In addition to more conventional gel-electrophoresis and DNA sequencing, mutations can also be detected by in situ analysis.

The sequences of the present invention are also valuable for chromosome identification. The sequence is specifically targeted to and can hybridize with a particular location on an individual human chromosome. Moreover, there is a current need for identifying particular sites on the chromosome. Few chromosome marking reagents based on actual sequence data (repeat polymorphisms) are presently available for marking chromosomal location. The mapping of DNAs to chromosomes according to the present invention is an important first step in correlating those sequences with genes associated with disease.

Briefly, sequences can be mapped to chromosomes by preparing PCR primers (preferably 15-25 bp) from the cDNA. Computer analysis of the 3' untranslated region is used to rapidly select primers that do not span more than one exon in the genomic DNA, thus complicating the amplification process. These primers are then used for PCR screening of somatic cell hybrids containing individual human chromosomes. Only those hybrids containing the human gene corresponding to the primer will yield an amplified fragment.

PCR mapping of somatic cell hybrids is a rapid procedure for assigning a particular DNA to a particular chromosome. Using the present invention with the same oligonucleotide primers, sublocalization can be achieved with panels of fragments from specific chromosomes or pools of large genomic clones in an analogous manner. Other mapping strategies that can similarly be used to map to its chromosome include in situ hybridization, prescreening with labeled flow-sorted chromosomes and preselection by hybridization to construct chromosome specific-cDNA libraries.

Fluorescence in situ hybridization (FISH) of a cDNA clone to a metaphase chromosomal spread can be used to provide a precise chromosomal location in one step. This technique can be used with cDNA as short as 500 or 600 bases; however, clones larger than 2,000 bp have a higher likelihood of binding to a unique chromosomal location with sufficient signal intensity for simple detection. FISH requires use of the clones from which the expression sequence tag was derived, and the longer the Better. For example, 2,000 bp is good, 4,000 is better, and more than 4,000 is probably not necessary to get good results a reasonable percentage of the time. For a review of this technique, see Verma et al., Human Chromosomes: a Manual of Basic Techniques, Pergamon Press, New York (1988).

Once a sequence has been mapped to a precise chromosomal location, the physical position of the sequence on the chromosome can be correlated with genetic map data. Such data are found, for example, in V. McKusick, Mendelian Inheritance in Man (available on line through Johns Hopkins University Welch Medical Library). The relationship between genes and diseases that have been mapped to the same chromosomal region are then identified through linkage analysis (coinheritance of physically adjacent genes).

Next, it is necessary to determine the differences in the cDNA or genomic sequence between affected and unaffected individuals. If a mutation is observed in some or all of the affected individuals but not in any normal individuals, then the mutation is likely to be the causative agent of the disease.

With current resolution of physical mapping and genetic mapping techniques, a cDNA precisely localized to a chromosomal region associated with the disease could be one of between 50 and 500 potential causative genes. (This assumes 1 megabase mapping resolution and one gene per 20 kb).

The polypeptides, their fragments or other derivatives, or analogs thereof, or cells expressing them can be used as an immunogen to produce antibodies thereto. These antibodies can be, for example, polyclonal or monoclonal antibodies. The present invention also includes chimeric, single chain, and humanized antibodies, as well as Fab fragments, or the product of an Fab expression library. Various procedures known in the art may be used for the production of such antibodies and fragments.

Antibodies generated against the polypeptides corresponding to a sequence of the present invention can be obtained by direct injection of the polypeptides into an animal or by administering the polypeptides to an animal, preferably a nonhuman. The antibody so obtained will then bind the polypeptides itself. In this manner, even a sequence encoding only a fragment of the polypeptides can be used to generate antibodies binding the whole native polypeptides. Such antibodies can then be used to isolate the polypeptide from tissue expressing that polypeptide.

For preparation of monoclonal antibodies, any technique which provides antibodies produced by continuous cell line cultures can be used. Examples include the hybridoma technique (Kohler and Milstein, 1975, Nature, 256:495-497), the trioma technique, the human B-cell hybridoma technique (Kozbor et al., 1983, Immunology Today 4:72), and the EBV-hybridoma technique to produce human monoclonal antibodies (Cole, et al., 1985, in Monoclonal Antibodies and Cancer Therapy, Alan R. Liss, Inc., pp. 77-96).

Techniques described for the production of single chain antibodies (U.S. Pat. No. 4,946,778) can be adapted to produce single chain antibodies to immunogenic polypeptide products of this invention. Also, transgenic mice may be used to express humanized antibodies to immunogenic polypeptide products of this invention.

The present invention will be further described with reference to the following examples; however, it is to be understood that the present invention is not limited to such examples. All parts or amounts, unless otherwise specified, are by weight.

In order to facilitate understanding of the following examples certain frequently occurring methods and/or terms will be described.

"Plasmids" are designated by a lower case p preceded and/or followed by capital letters and/or numbers. The starting plasmids herein are either commercially available, publicly available on an unrestricted basis, or can be constructed from available plasmids in accord with published procedures. In addition, equivalent plasmids to those described are known in the art and will be apparent to the ordinarily skilled artisan.

"Digestion" of DNA refers to catalytic cleavage of the DNA with a restriction enzyme that acts only at certain sequences in the DNA. The various restriction enzymes used herein are commercially available and their reaction conditions, cofactors and other requirements were used as would be known to the ordinarily skilled artisan. For analytical purposes, typically 1 μg of plasmid or DNA fragment is used with about 2 units of enzyme in about 20 μl of buffer solution. For the purpose of isolating DNA fragments for plasmid construction, typically 5 to 50 μg of DNA are digested with 20 to 250 units of enzyme in a larger volume. Appropriate buffers and substrate amounts for particular restriction enzymes are specified by the manufacturer. Incubation times of about 1 hour at 37° C. are ordinarily used, but may vary in accordance with the supplier's instructions. After digestion the reaction is electrophoresed directly on a polyacrylamide gel to isolate the desired fragment.

Size separation of the cleaved fragments is performed using 8 percent polyacrylamide gel described by Goeddel, D. et al., Nucleic Acids Res., 8:4057 (1980).

"Oligonucleotides" refers to either a single stranded polydeoxynucleotide or two complementary polydeoxynucleotide strands which may be chemically synthesized. Such synthetic oligonucleotides have no 5' phosphate and thus will not ligate to another oligonucleotide without adding a phosphate with an ATP in the presence of a kinase. A synthetic oligonucleotide will ligate to a fragment that has not been dephosphorylated.

"Ligation" refers to the process of forming phosphodiester bonds between two double stranded nucleic acid fragments (Maniatis, T., et al., Id., p. 146). Unless otherwise provided, ligation may be accomplished using known buffers and conditions with 10 units of T4 DNA ligase ("ligase") per 0.5 μg of approximately equimolar amounts of the DNA fragments to be ligated.

Unless otherwise stated, transformation was performed as described in the method of Graham, F. and Van der Eb, A., Virology, 52:456-457 (1973).

EXAMPLES Example 1

Bacterial Expression and Purification of Human Amine Transporter

The DNA sequence encoding human amine transporter, ATCC # 75980, is initially amplified using PCR oligonucleotide primers corresponding to the 5' and 3' end sequences of the processed amine transporter nucleic acid sequence (minus the signal peptide sequence). Additional nucleotides corresponding to amine transporter gene are added to the 5' and 3' sequences respectively. The 5' oligonucleotide primer has the sequence 5' GACTAAAGCTTAATGCTCCGGCCCATTCTG 3' (SEQ ID No. 3) contains a HindIII restriction enzyme site followed by 18 nucleotides of human amine transporter coding sequence starting from the presumed terminal amino acid of the processed protein. The 3' sequence 5' GAACTTCTAGACGGTCAGCCATGGTGACTGG 3' (SEQ ID No. 4) contains complementary sequences to an XbaI site and is followed by 20 nucleotides of the human amine transporter gene. The X restriction enzyme sites correspond to the restriction enzyme sites on the bacterial expression vector pQE-9 (Qiagen, Inc. Chatsworth, Calif.). pQE-9 encodes antibiotic resistance (AMp^(r)), a bacterial origin of replication (ori), an IPTG-regulatable promoter operator (P/O), a ribosome binding site (RBS), a 6-His tag and restriction enzyme sites. pQE-9 is then digested with HindIII and XbaI. The amplified sequences are ligated into pQE-9 and are inserted in frame with the sequence encoding for the histidine tag and the RBS. The ligation mixture is then used to transform E. coli strain M15/rep 4 (Qiagen, Inc.) by the procedure described in Sambrook, J. et al., Molecular Cloning: A Laboratory Manual, Cold Spring Laboratory Press, (1989). M15/rep4 contains multiple copies of the plasmid pREP4, which expresses the lacI repressor and also confers kanamycin resistance (Kan^(r)). Transformants are identified by their ability to grow on LB plates and ampicillin/kanamycin resistant colonies are selected. Plasmid DNA is isolated and confirmed by restriction analysis. Clones containing the desired constructs are grown overnight (O/N) in liquid culture in LB media supplemented with both Amp (100 ug/ml) and Kan (25 ug/ml). The O/N culture is used to inoculate a large culture at a ratio of 1:100 to 1:250. The cells are grown to an optical density 600 (O.D.⁶⁰⁰) of between 0.4 and 0.6. IPTG ("Isopropyl-B-D-thiogalacto pyranoside") is then added to a final concentration of 1 mM. IPTG induces by inactivating the lacI repressor, clearing the P/O leading to increased gene expression. Cells are grown an extra 3 to 4 hours. Cells are then harvested by centrifugation. The cell pellet is solubilized in the chaotropic agent 6 Molar Guanidine HCl. After clarification, solubilized human amine transporter is purified from this solution by chromatography on a Nickel-Chelate column under conditions that allow for tight binding by proteins containing the 6-His tag (Hochuli, E. et al., J. Chromatography 411:177-184 (1984)). Human amine transporter protein is eluted from the column in 6 molar guanidine HCl pH 5.0 and for the purpose of renaturation adjusted to 3 molar guanidine HCl, 100 mM sodium phosphate, 10 mmolar glutathione (reduced) and 2 mmolar glutathione (oxidized). After incubation in this solution for 12 hours the protein is dialyzed to 10 mmolar sodium phosphate.

Example 2

Cloning and expression of human amine transporter using the baculovirus expression system

The DNA sequence encoding the full length human amine transporter protein, ATCC # 75980, is amplified using PCR oligonucleotide primers corresponding to the 5' and 3' sequences of the gene:

The 5' primer has the sequence 5' CGGGATCCCTCCATGGCT CCGGCCCATTCTG 3' (SEQ ID No. 5) and contains a BamHI restriction enzyme site (in bold) followed by 4 nucleotides resembling an efficient signal for the initiation of translation in eukaryotic cells (Kozak, M., J. Mol. Biol., 196:947-950 (1987) which is just behind the first 18 nucleotides of the human amine transporter gene (the initiation codon for translation "ATG" is underlined).

The 3' primer has the sequence 5' CGGGATCCCGCT CAGCCATGGTGACTGGT 3' (SEQ ID No. 6) and contains the cleavage site for the restriction endonuclease BamHI and 18 nucleotides complementary to the 3' non-translated sequence of the human amine transporter gene. The amplified sequences are isolated from a 1% agarose gel using a commercially available kit ("Geneclean," BIO 101 Inc., La Jolla, Calif.). The fragment is then digested with the endonucleases BamHI and then purified again on a 1% agarose gel. This fragment is designated F2.

The vector pRG1 (modification of pVL941 vector, discussed below) is used for the expression of the human amine transporter protein using the baculovirus expression system (for review see: Summers, M. D. and Smith, G. E. 1987, A manual of methods for baculovirus vectors and insect cell culture procedures, Texas Agricultural Experimental Station Bulletin No. 1555). This expression vector contains the strong polyhedrin promoter of the Autographa californica nuclear polyhedrosis virus (AcMNPV) followed by the recognition sites for the restriction endonucleases BamHI. The polyadenylation site of the simian virus (SV)40 is used for efficient polyadenylation. For an easy selection of recombinant viruses the beta-galactosidase gene from E.coli is inserted in the same orientation as the polyhedrin promoter followed by the polyadenylation signal of the polyhedrin gene. The polyhedrin sequences are flanked at both sides by viral sequences for the cell-mediated homologous recombination of co-transfected wild-type viral DNA. Many other baculovirus vectors could be used in place of PRG1 such as pAc373, pVL941 and pAcIM1 (Luckow, V. A. and Summers, M. D., Virology, 170:31-39).

The plasmid is digested with the restriction enzymes BamHI and then dephosphorylated using calf intestinal phosphatase by procedures known in the art. The DNA is then isolated from a 1% agarose gel using the commercially available kit ("Geneclean" BIO 101 Inc., La Jolla, Calif.). This vector DNA is designated V2.

Fragment F2 and the dephosphorylated plasmid V2 are ligated with T4 DNA ligase. E.coli HB 101 cells are then transformed and bacteria identified that contained the plasmid (pBac-Human amine transporter) with the human amine transporter gene using the enzyme BamHI. The sequence of the cloned fragment is confirmed by DNA sequencing.

5 μg of the plasmid pBac-Human amine transporter is co-transfected with 1.0 μg of a commercially available linearized baculovirus ("BaculoGold™ baculovirus DNA", Pharmingen, San Diego, Calif.) using the lipofection method (Felgner et al. Proc. Natl. Acad. Sci. U.S.A., 84:7413-7417 (1987)).

1 μg of BaculoGold™ virus DNA and 5 μg of the plasmid pBac-Human amine transporter are mixed in a sterile well of a microtiter plate containing 50 μl of serum free Grace's medium (Life Technologies Inc., Gaithersburg, Md.). Afterwards 10 μl Lipofectin plus 90 μl Grace's medium are added, mixed and incubated for 15 minutes at room temperature. Then the transfection mixture is added drop-wise to the Sf9 insect cells (ATCC CRL 1711) seeded in a 35 mm tissue culture plate with 1 ml Grace's medium without serum. The plate is rocked back and forth to mix the newly added solution. The plate is then incubated for 5 hours at 27° C. After 5 hours the transfection solution is removed from the plate and 1 ml of Grace's insect medium supplemented with 10% fetal calf serum is added. The plate is put back into an incubator and cultivation continued at 27° C. for four days.

After four days the supernatant is collected and a plaque assay performed similar as described by Summers and Smith (supra). As a modification an agarose gel with "Blue Gal"(Life Technologies Inc., Gaithersburg) is used which allows an easy isolation of blue stained plaques. (A detailed description of a "plaque assay" can also be found in the user's guide for insect cell culture and baculovirology distributed by Life Technologies Inc., Gaithersburg, page 9-10)

Four days after the serial dilution, the viruses are added to the cells and blue stained plaques are picked with the tip of an Eppendorf pipette. The agar containing the recombinant viruses is then resuspended in an Eppendorf tube containing 200 μl of Grace's medium. The agar is removed by a brief centrifugation and the supernatant containing the recombinant baculovirus is used to infect Sf9 cells seeded in 35 mm dishes. Four days later the supernatants of these culture dishes are harvested and then stored at 4° C.

Sf9 cells are grown in Grace's medium supplemented with 10% heat-inactivated FBS. The cells are infected with the recombinant baculovirus V-Human amine transporter at a multiplicity of infection (MOI) of 2. Six hours later the medium is removed and replaced with SF900 II medium minus methionine and cysteine (Life Technologies Inc., Gaithersburg). 42 hours later 5 μCi of ³⁵ S-methionine and 5 μCi ³⁵ S cysteine (Amersham) are added. The cells are further incubated for 16 hours before they are harvested by centrifugation and the labelled proteins visualized by SDS-PAGE and autoradiography.

Example 3

Expression of Recombinant Human Amine Transporter in COS cells

The expression of plasmid, Human amine transporter HA is derived from a vector pcDNAI/Amp (Invitrogen) containing: 1) SV40 origin of replication, 2) ampicillin resistance gene, 3) E.coli replication origin, 4) CMV promoter followed by a polylinker region, a SV40 intron and polyadenylation site. A DNA fragment encoding the entire Human amine transporter precursor and a HA tag fused in frame to its 3' end is cloned into the polylinker region of the vector, therefore, the recombinant protein expression is directed under the CMV promoter. The HA tag correspond to an epitope derived from the influenza hemagglutinin protein as previously described (I. Wilson, et al., Cell, 37:767, (1984)). The infusion of HA tag to the target protein allows easy detection of the recombinant protein with an antibody that recognizes the HA epitope.

The plasmid construction strategy is described as follows:

The DNA sequence encoding Human amine transporter, ATCC # 75980, is constructed by PCR using two primers: the 5' primer 5' GTCCAAGCTTGCCACCATGCTGCGGCCCATTCTG 3' (SEQ ID No. 7) contains a HindIII site followed by 18 nucleotides of Human amine transporter coding sequence starting from the initiation codon; the 3' sequence 5' CTAGCTCGAGTCAGCCATGG TGACTGGTAGCGTAGTCTGGGACGTCGTATGGGTAGCA 3' (SEQ ID No. 8) contains complementary sequences to an XhoI site, translation stop codon, HA tag and the last 18 nucleotides of the Human amine transporter coding sequence (not including the stop codon). Therefore, the PCR product contains a HindIII site, human amine transporter coding sequence followed by HA tag fused in frame, a translation termination stop codon next to the HA tag, and an HindIII site. The PCR amplified DNA fragment and the vector, pcDNAI/Amp, are digested with HindIII and XhoI restriction enzyme and ligated. The ligation mixture is transformed into E. coli strain SURE (Stratagene Cloning Systems, La Jolla, Calif.) the transformed culture is plated on ampicillin media plates and resistant colonies are selected. Plasmid DNA is isolated from transformants and examined by restriction analysis for the presence of the correct fragment. For expression of the recombinant amine transporter, COS cells are transfected with the expression vector by DEAE-DEXTRAN method (J. Sambrook, E. Fritsch, T. Maniatis, Molecular Cloning: A Laboratory Manual, Cold Spring Laboratory Press, (1989)). The expression of the Human amine transporter HA protein is detected by radiolabelling and immunoprecipitation method (E. Harlow, D. Lane, Antibodies: A Laboratory Manual, Cold Spring Harbor Laboratory Press, (1988)). Cells are labelled for 8 hours with ³⁵ S-cysteine two days post transfection. Culture media is then collected and cells are lysed with detergent (RIPA buffer (150 mM NaCl, 1% NP-40, 0.1% SDS, 1% NP-40, 0.5% DOC, 50 mM Tris, pH 7.5) (Wilson, I. et al., Id. 37:767 (1984)). Both cell lysate and culture media are precipitated with a HA specific monoclonal antibody. Proteins precipitated are analyzed on 15% SDS-PAGE gels.

Example 4

Expression pattern of Human amine transporter in human tissue

Northern blot analysis is carried out to examine the levels of expression of Human amine transporter in human tissues. Total cellular RNA samples are isolated with RNAzol™ B system (Biotecx Laboratories, Inc. Houston, Tex.). About 10 μg of total RNA isolated from each human tissue specified is separated on 1% agarose gel and blotted onto a nylon filter (Sambrook, Fritsch, and Maniatis, Molecular Cloning, Cold Spring Harbor Press, (1989)). The labeling reaction is done according to the Stratagene Prime-It kit with 50 ng DNA fragment. The labeled DNA is purified with a Select-G-50 column (5 Prime-3 Prime, Inc. Boulder, Colo.). The filter is then hybridized with radioactive labeled full length Human amine transporter gene at 1,000,000 cpm/ml in 0.5M NaPO₄, pH 7.4 and 7% SDS overnight at 65° C. After wash twice at room temperature and twice at 60° C. with 0.5×SSC, 0.1% SDS, the filter is then exposed at -70° C. overnight with an intensifying screen.

Numerous modifications and variations of the present invention are possible in light of the above teachings and, therefore, within the scope of the appended claims, the invention may be practiced otherwise than as particularly described.

    __________________________________________________________________________     SEQUENCE LISTING     (1) GENERAL INFORMATION:     (iii) NUMBER OF SEQUENCES: 9     (2) INFORMATION FOR SEQ ID NO:1:     (i) SEQUENCE CHARACTERISTICS:     (A) LENGTH: 2885 base pairs     (B) TYPE: nucleic acid     (C) STRANDEDNESS: double     (D) TOPOLOGY: linear     (ii) MOLECULE TYPE: cDNA     (ix) FEATURE:     (A) NAME/KEY: CDS     (B) LOCATION: 719..2128     (xi) SEQUENCE DESCRIPTION: SEQ ID NO:1:     TCCTGCGTTATCCCCCTGATTCTGTGGATAACCGTATTNCCGCCTTTGAGTGAGCTGATA60     CCGCTCNCCNCAGCCGAACGACCGAGCGCAGCGAGTCAGTGAGCGAGGAAGCGGAAGAGC120     GCCCAATACGCAAACCGCCTCTCCCCGCGCGTTGGCCGATTCATTAATGCAGCTGGCACG180     ACAGGTTTCCCGACTGGAAAGCGGGCAGTGAGCGCAACGCAATTAATGTGAGTTAGCTCA240     CTCATTAGGCACCCCAGGCTTTACACTTTATGCTTCCGGCTCGTATGTTGTGTGGAATTG300     TGAGCGGATAACAATTTCACACAGGAAACAGCTATGACCATGATTACGCCAAGCTCGAAA360     TTAACCCTCACTAAAGGGAACAAAAGCTGGAGCTCCACCGCGGTGGCGNCCGCTCTAGAA420     CTAGTGGATCCCCCGGNCTGCAGGGGCACACACACGCACACATACACAGAATCCTCAGAT480     AACAGGAGGCAATAAATCCAACAGCACATCCACGTTCAGAGAACAGTGTCCCTGCTGTCT540     TGCTAACAGCTGCCAATACCTCACTGAGTGCCTCACACCAACATGGGCTCCAAGTGAGTT600     TCATTCGTCTGGGCAGACTCCCTCCCCTCTTCCATAAAGGCTGCAGGAGACCTGTAGCTG660     TCACAGGACCTTCCCTAAGAGCCCGCAGGGGGAAGACTGCCCCAGTCCGGCCATCACC718     ATGCTCCGGCCCATTCTGGATGCTCCCCAGCGGTTGCTGAAGGAGGGG766     MetLeuArgProIleLeuAspAlaProGlnArgLeuLeuLysGluGly     151015     AGAGCGTCCCGGCAGCTGGTGCTGGTGGTGGTATTCGTCGCTTTGCTC814     ArgAlaSerArgGlnLeuValLeuValValValPheValAlaLeuLeu     202530     CTGGACAACATGCTGTTTACTGTGGTGGTGCCAATTGTGCCCACCTTC862     LeuAspAsnMetLeuPheThrValValValProIleValProThrPhe     354045     CTATATGACATGGAGTTCAAAGAAGTCATCTCTTCTCTGCACCTCGGG910     LeuTyrAspMetGluPheLysGluValIleSerSerLeuHisLeuGly     505560     CATGCCGGAAGTTCCCCACATGCCCTCGCCTCTCCTGCCTTTTCCACC958     HisAlaGlySerSerProHisAlaLeuAlaSerProAlaPheSerThr     65707580     ATCTTCTCCTTCTTCAACAACAACACCGTGGCTGTTGAAGAAAGCGTA1006     IlePheSerPhePheAsnAsnAsnThrValAlaValGluGluSerVal     859095     CCTAGTGGAATAGCATGGATGAATGACACTGCCAGCACCATCCCACCT1054     ProSerGlyIleAlaTrpMetAsnAspThrAlaSerThrIleProPro     100105110     CCAGCCACTGAAGCCATCTCAGCTCATAAAAACAACTGCTTGCAAGGC1102     ProAlaThrGluAlaIleSerAlaHisLysAsnAsnCysLeuGlnGly     115120125     ACAGGTTTCTTGGAGGAAGAGACTACCCGGGTCGGGGTTCTGTTTGCT1150     ThrGlyPheLeuGluGluGluThrThrArgValGlyValLeuPheAla     130135140     TCAAAGGCTGTGATGCAACTTCTGGTCAACCCATTCGTGGGCCCTCTC1198     SerLysAlaValMetGlnLeuLeuValAsnProPheValGlyProLeu     145150155160     ACCAACAGGATTGGATATCATATCCCCATGTTTGCTGGCTTTGTTATC1246     ThrAsnArgIleGlyTyrHisIleProMetPheAlaGlyPheValIle     165170175     ATGTTTCTCTCCACAGTTATGTTTGCTTTTTCTGGGACCTATACTCTA1294     MetPheLeuSerThrValMetPheAlaPheSerGlyThrTyrThrLeu     180185190     CTCTTTGTGGCCCGAACCCTTCAAGGCATTGGATCTTCATTTTCATCT1342     LeuPheValAlaArgThrLeuGlnGlyIleGlySerSerPheSerSer     195200205     GTTGCAGGTCTTGGAATGCTGGCCAGTGTCTACACTGATGACCATGAG1390     ValAlaGlyLeuGlyMetLeuAlaSerValTyrThrAspAspHisGlu     210215220     AGAGGACGAGCCATGGGAACTGCTCTGGGGGGCCTGGCCTTGGGGTTG1438     ArgGlyArgAlaMetGlyThrAlaLeuGlyGlyLeuAlaLeuGlyLeu     225230235240     CTGGTGGGAGCTCCCTTTGGAAGTGTAATGTACGAGTTTGTTGGGAAG1486     LeuValGlyAlaProPheGlySerValMetTyrGluPheValGlyLys     245250255     TCTGCACCCTTCCTCATCCTGGCCTTCCTGGCACTACTGGATGGAGCA1534     SerAlaProPheLeuIleLeuAlaPheLeuAlaLeuLeuAspGlyAla     260265270     CTCCAGCTTTGCATCCTACAGCCTTCCAAAGTCTCTCCTGAGAGTGCC1582     LeuGlnLeuCysIleLeuGlnProSerLysValSerProGluSerAla     275280285     AAGGGGACTCCCCTCTTTATGCTTCTCAAAGACCCTTACATCCTGGTG1630     LysGlyThrProLeuPheMetLeuLeuLysAspProTyrIleLeuVal     290295300     GCTGCAGGGTCCATCTGCTTTGCCAACATGGGGGTGGCCATCCTGGAG1678     AlaAlaGlySerIleCysPheAlaAsnMetGlyValAlaIleLeuGlu     305310315320     CCCACACTGCCCATCTGGATGATGCAGACCATGTGCTCCCCCAAGTGG1726     ProThrLeuProIleTrpMetMetGlnThrMetCysSerProLysTrp     325330335     CAGCTGGGTCTAGCTTTCTTGCCTGCCAGTGTGTCCTACCTCATTGGC1774     GlnLeuGlyLeuAlaPheLeuProAlaSerValSerTyrLeuIleGly     340345350     ACCAACCTCTTTGGTGTGTTGGCCAACAAGATGGGTCGGTGGCTGTGT1822     ThrAsnLeuPheGlyValLeuAlaAsnLysMetGlyArgTrpLeuCys     355360365     TCCCTAATCGGGATGCTGGTAGTAGGTACCAGCTTGCTCTGTGTTCCT1870     SerLeuIleGlyMetLeuValValGlyThrSerLeuLeuCysValPro     370375380     CTGGCTCACAAAAATTTTGGTCTCATTGGCCCCAATGCAGGGCTTGGC1918     LeuAlaHisLysAsnPheGlyLeuIleGlyProAsnAlaGlyLeuGly     385390395400     CTTNCCATAGGCATGGTGGAATCTTCTATGATGCCCATCATGGGGCAC1966     LeuXaaIleGlyMetValGluSerSerMetMetProIleMetGlyHis     405410415     CTGGTGGATCCACGCCACACCTCGGTGTATGGGAGTGTCCACGCCATC2014     LeuValAspProArgHisThrSerValTyrGlySerValHisAlaIle     420425430     GCTGATGTGGCTTTTTGCATGGGCTTTGCTATAGGCTATTCTGAGTCA2062     AlaAspValAlaPheCysMetGlyPheAlaIleGlyTyrSerGluSer     435440445     GGACTGCCCCATGGAGACCCGGATGTATCAACCCAGAAACCTCTTCCC2110     GlyLeuProHisGlyAspProAspValSerThrGlnLysProLeuPro     450455460     TGGACCAGTCACCATGGCTGACCCACGGCTCAGTGGCCTCAAAACCTC2158     TrpThrSerHisHisGly     465470     TGCCTGGGATCTTCTTCCTCCCCTCCCATGGAGACTGTCCCTCATACTCTTCTCACCTGT2218     GTAACTTGTAGCTCTTCMTCTATGCCTTGGTGCCGCAGTGGCCCATCTTTTATGGGAAGA2278     CAGAGTGATGCACCYYCCCGCTGCTGTGAGGTTGATTAAACTTGAGCTGTGACGGGGTTC2338     TGCAAGGGGTGACTCATTGYATAGAGGTGGTAGTGAGTAATGTGCCCCTGAAACCAGTGG2398     GGTGACTGACAAGCCTCTTTAATCTGTTGCCTGATTTTCTCTGGCATAGCCCCAACAGAT2458     CGGAAGAGTGTTACCCTCTTTWCCCTCAACGTGTTCTTTCCCGGGTTTTCCCCAGCCGAG2518     TTGAGAAAATGTTCTCAGCATTGTCTTGCTGCCAAATGCCAGCKTGAAGAGTTWGGTATG2578     KTTTTTCTNCCATTTATTTTATTTATTWACTAAAGTGAATGATTTTACTGTGGYTAAATC2638     TAGAGCTGCTAAAAGGGCTTTACCCTCAGTGAAAAGTGTCTTCTATTTNCATWATCTTTC2698     AGAAACWGGAGCCCATTTCTCTTCTGGTGGAGTTATNGACATCCTCCTGACCNCCCCTGT2758     GTNTNCCTACCTNTACTGAACCTCTTAGACTCTNAGAAATAAAAGTAGAAGAAAGACAGA2818     AAAATTAACTGATTAGACCCAAGATTTCATGGGAAGAAGTTAAAAGAAACTGCCTTGGAA2878     ATCCCTC2885     (2) INFORMATION FOR SEQ ID NO:2:     (i) SEQUENCE CHARACTERISTICS:     (A) LENGTH: 470 amino acids     (B) TYPE: amino acid     (D) TOPOLOGY: linear     (ii) MOLECULE TYPE: protein     (xi) SEQUENCE DESCRIPTION: SEQ ID NO:2:     MetLeuArgProIleLeuAspAlaProGlnArgLeuLeuLysGluGly     151015     ArgAlaSerArgGlnLeuValLeuValValValPheValAlaLeuLeu     202530     LeuAspAsnMetLeuPheThrValValValProIleValProThrPhe     354045     LeuTyrAspMetGluPheLysGluValIleSerSerLeuHisLeuGly     505560     HisAlaGlySerSerProHisAlaLeuAlaSerProAlaPheSerThr     65707580     IlePheSerPhePheAsnAsnAsnThrValAlaValGluGluSerVal     859095     ProSerGlyIleAlaTrpMetAsnAspThrAlaSerThrIleProPro     100105110     ProAlaThrGluAlaIleSerAlaHisLysAsnAsnCysLeuGlnGly     115120125     ThrGlyPheLeuGluGluGluThrThrArgValGlyValLeuPheAla     130135140     SerLysAlaValMetGlnLeuLeuValAsnProPheValGlyProLeu     145150155160     ThrAsnArgIleGlyTyrHisIleProMetPheAlaGlyPheValIle     165170175     MetPheLeuSerThrValMetPheAlaPheSerGlyThrTyrThrLeu     180185190     LeuPheValAlaArgThrLeuGlnGlyIleGlySerSerPheSerSer     195200205     ValAlaGlyLeuGlyMetLeuAlaSerValTyrThrAspAspHisGlu     210215220     ArgGlyArgAlaMetGlyThrAlaLeuGlyGlyLeuAlaLeuGlyLeu     225230235240     LeuValGlyAlaProPheGlySerValMetTyrGluPheValGlyLys     245250255     SerAlaProPheLeuIleLeuAlaPheLeuAlaLeuLeuAspGlyAla     260265270     LeuGlnLeuCysIleLeuGlnProSerLysValSerProGluSerAla     275280285     LysGlyThrProLeuPheMetLeuLeuLysAspProTyrIleLeuVal     290295300     AlaAlaGlySerIleCysPheAlaAsnMetGlyValAlaIleLeuGlu     305310315320     ProThrLeuProIleTrpMetMetGlnThrMetCysSerProLysTrp     325330335     GlnLeuGlyLeuAlaPheLeuProAlaSerValSerTyrLeuIleGly     340345350     ThrAsnLeuPheGlyValLeuAlaAsnLysMetGlyArgTrpLeuCys     355360365     SerLeuIleGlyMetLeuValValGlyThrSerLeuLeuCysValPro     370375380     LeuAlaHisLysAsnPheGlyLeuIleGlyProAsnAlaGlyLeuGly     385390395400     LeuXaaIleGlyMetValGluSerSerMetMetProIleMetGlyHis     405410415     LeuValAspProArgHisThrSerValTyrGlySerValHisAlaIle     420425430     AlaAspValAlaPheCysMetGlyPheAlaIleGlyTyrSerGluSer     435440445     GlyLeuProHisGlyAspProAspValSerThrGlnLysProLeuPro     450455460     TrpThrSerHisHisGly     465470     (2) INFORMATION FOR SEQ ID NO:3:     (i) SEQUENCE CHARACTERISTICS:     (A) LENGTH: 30 base pairs     (B) TYPE: nucleic acid     (C) STRANDEDNESS: single     (D) TOPOLOGY: linear     (ii) MOLECULE TYPE: cDNA     (xi) SEQUENCE DESCRIPTION: SEQ ID NO:3:     GACTAAAGCTTAATGCTCCGGCCCATTCTG30     (2) INFORMATION FOR SEQ ID NO:4:     (i) SEQUENCE CHARACTERISTICS:     (A) LENGTH: 31 base pairs     (B) TYPE: nucleic acid     (C) STRANDEDNESS: single     (D) TOPOLOGY: linear     (ii) MOLECULE TYPE: cDNA     (xi) SEQUENCE DESCRIPTION: SEQ ID NO:4:     GAACTTCTAGACGGTCAGCCATGGTGACTGG31     (2) INFORMATION FOR SEQ ID NO:5:     (i) SEQUENCE CHARACTERISTICS:     (A) LENGTH: 31 base pairs     (B) TYPE: nucleic acid     (C) STRANDEDNESS: single     (D) TOPOLOGY: linear     (ii) MOLECULE TYPE: cDNA     (xi) SEQUENCE DESCRIPTION: SEQ ID NO:5:     CGGGATCCCTCCATGGCTCCGGCCCATTCTG31     (2) INFORMATION FOR SEQ ID NO:6:     (i) SEQUENCE CHARACTERISTICS:     (A) LENGTH: 29 base pairs     (B) TYPE: nucleic acid     (C) STRANDEDNESS: single     (D) TOPOLOGY: linear     (ii) MOLECULE TYPE: cDNA     (xi) SEQUENCE DESCRIPTION: SEQ ID NO:6:     CGGGATCCCGCTCAGCCATGGTGACTGGT29     (2) INFORMATION FOR SEQ ID NO:7:     (i) SEQUENCE CHARACTERISTICS:     (A) LENGTH: 34 base pairs     (B) TYPE: nucleic acid     (C) STRANDEDNESS: single     (D) TOPOLOGY: linear     (ii) MOLECULE TYPE: cDNA     (xi) SEQUENCE DESCRIPTION: SEQ ID NO:7:     GTCCAAGCTTGCCACCATGCTGCGGCCCATTCTG34     (2) INFORMATION FOR SEQ ID NO:8:     (i) SEQUENCE CHARACTERISTICS:     (A) LENGTH: 58 base pairs     (B) TYPE: nucleic acid     (C) STRANDEDNESS: single     (D) TOPOLOGY: linear     (ii) MOLECULE TYPE: cDNA     (xi) SEQUENCE DESCRIPTION: SEQ ID NO:8:     CTAGCTCGAGTCAGCCATGGTGACTGGTAGCGTAGTCTGGGACGTCGTATGGGTAGCA58     (2) INFORMATION FOR SEQ ID NO:9:     (i) SEQUENCE CHARACTERISTICS:     (A) LENGTH: 465 amino acids     (B) TYPE: amino acid     (C) STRANDEDNESS: Not Relevant     (D) TOPOLOGY: linear     (ii) MOLECULE TYPE: peptide     (xi) SEQUENCE DESCRIPTION: SEQ ID NO:9:     MetLeuGlnValValLeuGlyAlaProGlnArgLeuLeuLysGluGly     151015     ArgGlnSerArgLysLeuValLeuValValValPheValAlaLeuLeu     202530     LeuAspAsnMetLeuLeuThrValValValProIleValProThrPhe     354045     LeuTyrAlaThrGluPheLysAspSerAsnSerSerLeuHisArgGly     505560     ProSerValSerSerGlnGlnAlaLeuThrSerProAlaPheSerThr     65707580     IlePheSerPhePheAspAsnThrThrThrThrValGluGluHisVal     859095     ProPheArgValThrTrpThrAsnGlyThrIleProProProValThr     100105110     GluAlaSerSerValProLysAsnAsnCysLeuGlnGlyIleGluPhe     115120125     LeuGluGluGluAsnValArgIleGlyIleLeuPheAlaSerLysAla     130135140     LeuMetGlnLeuLeuValAsnProPheValGlyProLeuThrAsnArg     145150155160     IleGlyTyrHisIleProMetPheValGlyPheMetIleMetPheLeu     165170175     SerThrLeuMetPheAlaPheSerGlyThrTyrAlaLeuLeuPheVal     180185190     AlaArgThrLeuGlnGlyIleGlySerSerPheSerSerValAlaGly     195200205     LeuGlyMetLeuAlaSerValTyrThrAspAsnTyrGluArgGlyArg     210215220     AlaMetGlyIleAlaLeuGlyGlyLeuAlaLeuGlyLeuLeuValGly     225230235240     AlaProPheGlySerValMetTyrGluPheValGlyLysSerSerPro     245250255     PheLeuIleLeuAlaPheLeuAlaLeuLeuAspGlyAlaLeuGlnLeu     260265270     CysIleLeuTrpProSerLysValSerProGluSerAlaMetGlyThr     275280285     SerLeuLeuThrLeuLeuLysAspProTyrIleLeuValAlaAlaGly     290295300     SerIleCysLeuAlaAsnMetGlyValAlaIleLeuGluProThrLeu     305310315320     ProIleTrpMetMetGlnThrMetCysSerProGluTrpGlnLeuGly     325330335     LeuAlaPheLeuProAlaSerValAlaTyrLeuIleGlyThrAsnLeu     340345350     PheGlyValLeuAlaAsnLysMetGlyArgTrpLeuCysSerLeuVal     355360365     GlyMetValAlaValGlyIleSerLeuLeuCysValProLeuAlaHis     370375380     AsnIlePheGlyLeuIleGlyProAsnAlaGlyLeuGlyPheAlaIle     385390395400     GlyMetValAspSerSerLeuMetProIleMetGlyTyrLeuValAsp     405410415     LeuArgHisThrSerValTyrGlySerValTyrAlaIleAlaAspVal     420425430     AlaPheCysValGlyPheAlaIleGlyProSerThrGlyGlyValIle     435440445     ValGlnValIleGlyPheProTrpLeuMetValIleIleGlyThrIle     450455460     Asn     465     __________________________________________________________________________ 

What is claimed is:
 1. An isolated polypeptide having an amino acid sequence selected from the group consisting of:(a) amino acids 1 to 470 of SEQ ID NO:2; (b) amino acids 2 to 470 of SEQ ID NO:2; and (c) the amino acid sequence of the human amine transporter polypeptide having the amino acid sequence encoded by the cDNA clone contained in ATCC Deposit No.
 75980. 2. The isolated polypeptide of claim 1, wherein said polypeptide has the amino acid sequence of amino acids 1 to 470 of SEQ ID NO:2.
 3. The isolated polypeptide of claim 1, wherein said polypeptide has the amino acid sequence of amino acids 2 to 470 of SEQ ID NO:2.
 4. The isolated polypeptide of claim 1, wherein said polypeptide has the amino acid sequence as encoded by the cDNA clone contained in ATCC Deposit No.
 75980. 5. The isolated polypeptide of claim 1, which is produced or contained in a recombinant host cell.
 6. The isolated polypeptide of claim 5, wherein said recombinant host cell is mammalian.
 7. An isolated polypeptide encoded by a polynucleotide that hybridizes under stringent conditions with a polynucleotide of SEQ ID NO: 1 or the complement thereof, wherein said polypeptide retains substantially the same activity as a polypeptide having the amino acid sequence of amino acids 1 to 470 or 2 to 470 of SEQ ID NO:2.
 8. An isolated polypeptide wherein, except for one or more conservative amino acid substitutions, said polypeptide has a sequence selected from the group consisting of:(a) amino acids 1 to 470 of SEQ ID NO:2; and (b) amino acids 2 to 470 of SEQ ID NO:2, wherein said polypeptide retains substantially the same activity as a polypeptide having the amino acid sequence of amino acids 1 to 470 or 2 to 470 of SEQ ID NO:2. 